The present invention pertains to the art of molecular separation, specifically the physical separation or fractionating of molecular components of a gaseous mixtures. The invention finds particular application in the separation of oxygen from the other components of atmospheric air to supply oxygen to welding equipment and will be described with particular reference thereto. It is to be appreciated, however, that the present invention is also applicable to the separation of other gaseous mixtures and is particularly applicable to applications in which the segregated gases are to be supplied at relatively high pressures.
Heretofore, components have been separated or fractionated from gaseous mixtures utilizing a method and apparatus generally as described in U.S. Pat. No. 2,944,627, issued July 12, 1960 to Charles W. Skarstrom. The Skarstrom system pressurized the gaseous mixture to be fractionated with a compressor or the like. A crossover valving assembly channelled the pressurized gaseous mixture alternately to first and second vessels containing a molecular separation material. The crossover valving assembly further connected the vessel which was not receiving the gaseous mixture with a waste gas or secondary product discharge port. The molecular separation material selectively adsorbed one or more components of the gas and passed one or more other components connoted as a primary product gas. The primary product gas which passed through the vessel was channelled in part to a primary product outlet and in part to the other vessel. The primary product gas portion channelled to the other vessel flushed the adsorbed or secondary product gases therefrom out the secondary product discharge port. Cyclically, the crossover valving assembly switched the connection of the vessels with the incoming gaseous mixture and the secondary product discharge port. This cyclic switching of the vessels provided a continuing, though cyclically surging, flow of the primary product gas. Because the flow rate of the primary product gas varied at different portions of the cyclic switching cycle, a surge tank was commonly connected with the outlet so that a relatively even product flow would be provided by the apparatus.
For welding and other industrial operations, oxygen is supplied at 45 psi or better. In order to maintain a 45 psi pressure in the surge tank and compensate for a pressure drop across the vessels, the input compressor was required to supply the gaseous mixture to the vessels at about 65 psi. To produce oxygen at an average rate of 10 cubic feet per hour required about a one horsepower compressor. Higher oxygen supply rates required correspondingly higher horsepower compressors.
One of the drawbacks of the prior art oxygen generators for supplying oxygen to welding equipment was the relatively large amount of electrical or other energy consumed by the compressor. Another drawback was that the amount and pressure of output oxygen varied or surged during the production system as the vessels were switched. Yet another drawback was that the compressor was required to supply gas at about 65 psi to maintain about 45 psi in the surge tank.
The present invention contemplates a new and improved gas fractioning apparatus and method which provides primary product more efficiently, at a higher pressure, and with less energy consumption.